Calorific measurements have for many years been carried out by means of either adiabatic or isothermal bomb calorimeter systems. Both of these systems employ a bomb in which the sample of material to be tested is burnt in oxygen under high pressure, a calorimeter vessel in which the bomb is immersed in water, temperature measuring means in the water and a stirrer for circulating the water in the vessel. In the isothermal system the calorimeter vessel is located within an isothermal stirred water jacket from which it is insulated by an air space and in the adiabatic system the vessel and bomb are located in a stirred water jacket which completely surrounds and is separated from the vessel by an air space.
In both systems it is necessary to provide elaborate means for controlling the water jacket temperature. With the isothermal system it is necessary to maintain a substantially constant jacket temperature and with the adiabatic system the temperature controlling means must be capable of rapidly adjusting the jacket temperature to eliminate temperature differentials between the jacket and calorimeter for accurate adiabatic operation.
Because of the high degree of accuracy necessary from control systems such as heaters, stirrers and the like and the number of measurable variables such as water quantities and temperatures which have to be accurately and constantly measured and monitored during the testing of a sample, the systems are cumbersome and time consuming to operate. Additionally, because of the number of variables which have constantly to be monitored and errors which they themselves introduce to the system, and this includes ambient temperatures variations in which the systems are operated, the accuracy of the results of the tests using these systems are often questionable.